A non-volatile memory (NVM) or non-volatile storage is a computer memory that can retain the stored information even when not powered. Examples of a non-volatile memory include a read-only memory (ROM), a programmable read-only memory (PROM), an erasable programmable read-only memory (EPROM), an electrically erasable programmable read-only memory (EEPROM) and/or flash memories. PROMs are typically only once programmable, whereas EPROMs can be programmed and erased several times. The “programming” is also referred to as writing information to the memory or storing information in the memory. Prior to programming, the EPROMs are typically erased. The term “erased” is also referred to as deleting the information stored in the EPROM. Among the EPROMs, there are different classes of technology, for example, ultraviolet erasable PROMs or electrically erasable PROMs. In both technologies, an electrical charge is trapped when programming the EPROM. However, for ultraviolet (UV) erasable PROMs (UV EPROM), the trapped charge is removed by applying an ultraviolet light for a certain period, returning the entire memory to its original “blank” or in other words uncharged state. Electrically erasable PROMs have the advantage of being able to selectively erase any part of the memory without the need to erase the entire memory. Similar to the UV EPROMs, the trapped charges are released so that the selected part, for example, a single cell of the memory, returns to its original blank or uncharged state.
It is desirable to reduce the area or surface consumption of such programmable read-only memories.